Typically they go to Chiang Khong, where there are some wishy washy goings on. You can go to the Sop Ruak border crossing at the Golden Triangle and bounce back in less than an hour.
if your local immigration office won't, then drag your wife and paperwork to the next immigration office in the next district that will grant this extension, stay in a hotel that will file a TM30 and then go apply for the 60 day visit Thai family extension.